The invention refers to a device for the determination and/or control of a certain charging level of a material charged into a container. The device employs a vibration structure having two torsional vibrators of the same resonance frequency with vibration elements arranged in the opposite sense of rotation, arranged coaxially and enveloping each other at a distance from each other. The vibration structure has its vibrations damped by the outer vibration element enveloping the inner vibration element when contacting the charged material. Systems are provided to trigger indicating and/or switching processes as a function of the amplitude of the vibrations.
Devices of this kind are known. The effect is utilized that vibration energy is transferred from the vibration structure to the material charged by means of impulse transfer whereby the vibration structure which is stimulated towards vibrating is exposed to a damping effect.
Devices are known from the German Patent No. 582 760 and from the British Patent No. 10 13 186 in which a vibration rod excited to perform flexural vibrations at is resonance frequency projects into a container to be monitored and its vibrations are exposed to a damping effect when contacting the material charged so that the charging level is indicated by means of the change in vibrations.
However, these charging level measuring devices have the disadvantage that the single vibration rod exerts considerable alternating forces on the clamping system and thus on the container wall so that vibration energy is transferred from the vibration rod to the container wall. Owing to these losses, the vibration driving system must be designed with a high output in order to maintain vibrations. This, in its turn, has the effect that the vibration structure, when immersed in light weight bulk goods having a slight damping capability, is no longer sufficiently damped. An exact monitoring is, thus, not quite possible.
Therefore, a proposal was submitted having, instead of one vibration rod, two vibration rods, arranged in parallel next to each other, and projecting into the container, which are connected to each other by a crossbar at the clamping point and can be made to have opposing flexural vibrations (German Disclosure Publication No. 17 73 815). Besides the considerably greater structural complexity in comparison with the measuring devices for a single vibration rod, the device designed as a tuning fork has the disadvantage that powder-like or fiber-like goods to be charged can get caught between the vibration rods or grain can deposit there so that a damping of the vibration structure is effected even though the charging level is low.
Therefore, proposals have been submitted to provide vibration structures with two vibration elements arranged on top of each other which are designed as torsional vibrators having the same resonance frequency and are excited to perform vibrations in an opposite sense of rotation in order to determine the charging level. For this purpose, the vibration elements arranged coaxially towards each other can partially envelope each other for a distance.
Through a corresponding arrangement, advantages have been achieved to permit an exceedingly precise monitoring of the charging level in a container without transferring vibration energy to the container wall without requiring a complex structure.